In general, a crawler mounted construction machine having a pair of crawlers includes hydraulic equipments such as a pair of traveling hydraulic motor for driving each of the crawlers, a pair of hydraulic pumps for supplying driving pressure to each of the hydraulic motors, and a pair of control valves for controlling the flow of pressure oil from each hydraulic pump to each hydraulic motor.
It is desired that control valve sections installed in such a crawler mounted construction machine, for instance, a crawler mounted hydraulic excavator can also be used in a wheeled construction machine, such as a wheeled hydraulic excavator from a viewpoint of cost reduction. When the control valve sections of the crawler mounted hydraulic excavator are to be used in the wheeled hydraulic excavator, the pressure oil from each of the hydraulic pumps is made to flow together in the downstream of the control valve, and then this mixed oil is supplied to the hydraulic motor for wheels. As a result, the hydraulic motor rotates at high-speed to achieve the high-speed travel of the wheeled hydraulic excavator.
However, since confluence of the pressure oil is required due to the use of a pair of control valves with the wheeled hydraulic excavator which is generally equipped with only one traveling hydraulic motor, the circuit structure of the traveling system becomes complex.
Moreover, the number of actuators of the wheeled hydraulic excavator is likely to increase compared with the crawler mounted hydraulic excavator because various work attachments can be installed in the wheeled hydraulic excavator. However, increase in the number of actuators requires additional control valves, and thus the control valve sections of the crawler mounted hydraulic excavator cannot be used without any modifications, thereby causing the cost to increase.